The present invention generally relates to equipment adapted for supporting articles. More particularly, this invention relates to a self-aligning support assembly capable of supporting a cylindrical component, and in particular large rotatable cylindrical components such as during the manufacture, inspection, and/or servicing of rotors and shafts of turbomachinery, generators, and other axisymmetric components.
Depending on particular operating conditions, rotors used in steam turbines, gas turbines, and jet engines can have assembled or monolithic constructions. For example, large steam turbines typically have a bolted construction made up of separate rotors, each having a shaft with an integrally-formed wheel whose rim is configured for mounting buckets (blades). The configuration and composition of each separate rotor segment are chosen for the particular section of the turbine (for example, high pressure and low pressure stages) in which the segment will be located. Rotors for gas turbines and jet engines are often constructed by bolting a series of disks and shafts together. Another rotor construction involves welding together rotor segments formed of dissimilar materials, forming what may be termed a multiple alloy rotor (MAR). Monolithic multiple alloy rotors have also been proposed.
Turbine rotors operate at high rotational speeds in a thermally-hostile environment. Though significant advancements have been made in alloys to achieve long service lives, wear, erosion, corrosion, shock, fatigue and/or overstress may occur, necessitating periodic inspection and, if necessary, repair or replacement of a rotor or shaft. Inspection and servicing of turbine components typically entail mounting the component in a lathe or similar apparatus adapted to rotate the component about its axis, for example, during cleaning, dimensional inspection, nondestructive examination (NDE), disassembly/assembly, and machining. The component is often supported from beneath with rollers that help support the weight of the component without interfering with its ability to rotate. Rollers used for this purpose are typically hardened to resist deformation and hold tolerances under the weight of the component. The non-pliant nature of hard rollers necessitates a long and careful setup to ensure proper alignment of the rollers to the component, including precisely orienting the axes of the rollers parallel to the component. For example, hard roller assemblies are often “blued-in” by applying layout dye to the surfaces of the component, and then adjusting the rollers to achieve a uniform pattern in the dye. As an alternative, soft rollers can be used that are sufficiently compliant to better tolerate misalignments. In some situations, soft rollers are used in an unaligned condition, in which case the surfaces of the rollers are sacrificial. While simplifying setup, soft rollers can be incapable of holding sufficiently tight tolerances for such operations as dimensional inspect and machining.
In view of the above, it would be desirable if the process of aligning hard rollers to a rotor component could be simplified without degrading the dimensional accuracy normally required of hard rollers when supporting a rotor during inspection and servicing.